1. Field of the Invention
The present invention relates to manufacture of a display panel such as an organic electroluminescence (hereinafter simply referred to as “EL”) display panel and, in particular, to a sealing structure in the display panel.
2. Description of the Related Art
Plasma display panels (PDP) and liquid crystal display devices (LCD) are becoming widely available as thin flat display panels and organic EL panels are commercially available.
In an organic EL panel, an organic material is used as a light emitting material in each pixel or the like. Because the lifetime of the organic material is shortened when the organic material contains moisture, it is necessary to minimize an amount of moisture in a space in which the pixel is present. For this purpose, a sealing substrate is disposed to oppose, with a predetermined gap, an EL substrate on which display pixels including EL elements are formed in a matrix form and the peripheral portion of the substrates is air-tightly sealed with a sealing material made of a resin to prevent moisture from intruding into the inside. In addition, a desiccant is provided in the inside space to remove moisture.
As the sealing material, an epoxy-based ultraviolet curable resin or the like is used. However, in order to further improve the air-tightness, a method is proposed which uses a low-melting-point glass such as a solder glass (for example, Japanese Patent Laid-Open Publication No. 2001-319775).
In Japanese Patent Laid-Open Publication No. 2001-319775, a low-melting-point glass for joining substrates is sandwiched between glass substrates and is welded through heating. However, in such joining, it is difficult to precisely determine a line width and a position of the low-melting-point glass, and therefore, a sufficient margin must be provided in the joining portion. On the other hand, there is a demand for reducing the overall size of a display panel and to minimize an area of a peripheral region to be used for joining. There is another problem in that a distance between the substrates varies when an amount of the low-melting-point glass changes.